I think Rootboy is pretty close. The numbers make no sense and Motobecane used several factories all with slightly different methods further confusing things. Mine is a '71, dated only by component spec and thin evidence at that. Mine was made of 531 as have all the GR frames I have seen.

My GR came to me with a water bottle clamp on the seattube which had scraped up the paint quite a bit, including a vertical series of Zs right through the pretty red bands. I don't want to replicate that particular 'vintage' style, so am going sort of even more vintage: water bottle cage on a clamp on the handlebars. The old TA clamps are very expensive but VO makes one and it should be in my local LBS by now, actually two so my wife's mixte can have one, I'm also getting the VO cage. I'll report back!

Only negative is lack of water cage boss's ... Looks like this one had an clamp on at one time ... Any other ideas on carrying water....

I had a water bottle w/ a clamp, American Classic IIRC? I didn't care for it, as it scarred the paint job...even though I had put tape under the clamps. So I removed it. I also tried one of those handlebar cages, but found it threw the steering balance off when cruising at high speeds. All this was a long time ago & the bike doesn't see much riding time any more. I have other bikes that fill the need. I will say, it's one comfortable riding bike...!

One member here suggested using a 5mm rivnut to assimilate water-bottle bosses, but I wasn't esp fond of drilling into the frame.

Probably right dbakl. But, when did they stop painting the seat stay caps? I seem to think that was a very early feature, maybe ended in 73 or so, but my experience is limited. Cool bike. Love those lugs.

[QUOTE=Idkutet;14852695
Only negative is lack of water cage boss's ... Looks like this one had an clamp on at one time ... Any other ideas on carrying water.... My solution today was a bottle in the jersey[/QUOTE]

Water bottle bosses would be inappropriate on this bike, IMO. BTW, if you're worried about conventional, clamp on water bottle cages marring the finish, I've had good results by coating the inside of the clamps with clear Plasti-dip. A couple of very thin coats, let it dry very thoroughly, and you're good.

another great tip when securing smooth aluminum cage clamps to a pretty down tube is to use two sets of screws, one much longer than the other. first, use the long set to initially secure the clamps. and tighten. these screws should be way too long after the clamps are tightened. but the length of the screws will make initial setup a snap. then, after the clamps have been stretched and are in place, one by one, replace the screws with better fitting ones that are shorter. this method works perfectly, quickly, and will not lead to frustration and scratches of your downtube when trying to fit perfectly sized screws to your cage clamps.

will the velo orange french thread work on this frame? any other options?

It should, but you'd better make sure what Threads are exactly in your BB. My Grand Record has a Swiss BB w/ a left-hand threaded fixed cup. They are nearly impossible to find! However, Phil Wood has a Sealed BB's available w/ all the different cups...but cost $$.